Shear connection

A typical shear connection for a wall girt might consist of a relatively thin two bolt shear tab. As a blast load is applied to the girt, tearout of the tab may occur due to an inadequate number of bolts or insufficient weld capacity. This will prevent development of plastic moment capacity of the member and thus reduce its blast resistance. A typical upgrade for this type of connection is addition of a new shear tab wetded or bolted to the existing column and girt. 

The load-bearing behaviour of the bipartite beam with an elastic shear connection was first comprehensively researched by Mdhler [1]. It is typically used today in Germany in the design of timber-concrete composites with an elastic mechanical connection [2, 3]. 

Basically, the external bending moment Mei applied to the composite beam as a whole can be simplified into three component moments as follows. The two beam sections will be subjected to bending moments M and M2 proportional to their bending stiffnesses. The flexible shear connection will induce a compressive force N in the larger member and an equally large tensile force in the smaller member. These opposing forces, which act at a distance a apart, will lead to a third moment, the composite moment My = N a, which also contributes to the overall bending capacity (Fig. 1). 

Figure 1. The Gamma-method for a bipartite beam with an elastic shear connection The external bending moment Mg on the composite beam comprises three component moments Mi, M2 and My, which induce the stresses in the two members as shown above.

The Gamma method is named after the caitical factor Gamma y, which describes the relative stiffness of the elastic shear connection between the two members which form the bipartite beam. In a normal glulam beam, where the laminates are connected together with very stiff adhesive layers, y is 1.0 where there is no adhesive at all, and the two laminates are in no way connected to each other, y is zero. Our calculations indicate that the bipartite beam will attain the above optimal bending resistance only if the y value of the connection between the two members attains the corresponding ideal value ... 

Many of these applications will be considered further in Part 2 of the book, as will civil engineering uses of adhesives in a truly structural sense. By the latter it is implied that the adhesive is used to provide a shear connection between similar or dissimilar materials which enables the components being bonded to act as a composite structural unit. Within this definition, the main applications are ... 

Adhesives are often employed to achieve the necessary longitudinal shear connection for full composite action between the fresh and... 

A potential structural application of epoxy resin adhesives in bridge construction is to use them to form the necessary shear connection between steel girders and the concrete deck slab in composite bridges, in place of conventional welded mechanical fasteners. There are three ways in which bonded shear connections between steel and concrete might be achieved. 

Transverse continuity may be provided by using an in situ concrete connection containing looped reinforcement cast into the slabs (Fig. 8.3) an alternative arrangement using folded steel plates may also be used (Fig. 8.4). The primary shear connection is provided by shear studs welded alternately to the soffit plate and the longitudinal beam flange. It is important that the precast/i situ construction joint occurs well away from the beam flange to avoid excessive rotations and subsequent slab distress under traffic loads. 

When a cost-effective pultruded profile is used, mechanical means are needed to provide the shear connection with the concrete. 

Eawzia S, AI-Mahaidi R and Zhao X L (2006), Experimental and finite element analysis of a double lap shear connection between steel plates and CFRP , Compos Struct, 75(1-4), 156-162. 

Compared to common monolithic beams, composite beams with deformable shear connection present additional difficulties. Even in very simple structural systems (e.g., simply supported beams), complex distributions of the interface slip and force can develop. Different finite elements of composite beams with deformable shear connection have been developed and presented in the literature (Spacone El-Tawil 2004, Dall Asta 8c Zona 2004). These elements include suitable models describing section deformations in order to compute the section force resultants of steel-concrete composite members. This requires the use of realistic material constitutive models for beam steel, reinforcement steel, concrete, and shear-slip behaviour of the studs connecting the two structural components (Zona et al. 2005, 2006, Barbato et al. 2007). 

Zona, A., Barbato, M. Conte, J.P. 2005. Finite element response sensitivity analysis of steel-concrete composite beams with deformable shear connection. Journal of Engineering Mechanics (ASCE), 131(11) 1126-1139. 

A rectangular plate with dimensions Ipx x Ipy = 18.0 x 9.0 m stiffened by a rectangular beam of 1.0 m width eccentrically placed with respect to the center line of the plate (Fig. 4) has been studied (damping ratio = 1 = 0). In Table 1 the torsion 7 and warping 7 constants of the beam cross section and the values of the primary warping function (4>s)ff (/ = Ij 2) at the nodes of the two interface lines for various beam heights are presented. In Table 2 the computed first five eigenfrequencies, in Fig. 5 the fundamental modeshape and in Fig. 6 the deflection time history at point C (Fig. 4) of the stiffened plate for the cases of a partial in both directions and a full shear connection... 

Fig. 8 the deflection time history at point C (Fig. 7) of the stiffened plate subjected to the accelerogram of Athens Earthquake at September 7, 1999 for the cases of a partial in both directions and a full shear connection are presented as compared with those obtained from FEM solutions. 

Modeling of typical SCC beams beams with deformable shear connections Modeling of frames using beam elements... 

Explicit representation of the slip boundary conditions of the shear connection both at local and global levels... 

The present subchapter presents a simplified (new) modeling approach based on the work of Zhao et al. (2012) for the nonlinear analysis of SCC beams and composite frames with deformable shear connections (based on the distributed plasticity approach) using line elements to simulate the stmctural beam and column members, layered fiber section to simulate the reinforced concrete slabs, and nonlinear spring elements for the simulation of the interface between the stmctural steel beams and the reinforced concrete slab. Vertical interactions between the slab and steel beams are not expected to be significant, therefore are not accounted into the analysis. The geometry of the model, along with a simple set of details, is outlined below. The assembled model is shown in Fig. 1. 

Model Geometry of Beam with Deformable Shear Connection... 

Modeling of two-dimensional beams with deformable shear coimection is based on the Newmark et al. (1951) model, in which (i) the Euler-BemouUi beam theory applies to both components of the SCC beam and (ii) the deformable shear connection is represented by an interface model with distributed bond allowing interlayer slip as well as enforcing contact between the steel and concrete components. 

A simple two-dimensional 10 degree-of-fi eedom (DOF) see frame element with deformable shear connection is presented herein, similarly to Zona et al. (2008). With reference to Fig. 3, 8 of the lODOFs are external (4 DOFs per end node) allowing for the axial displacement, the transverse displacement, and the rotation of the steel beam and IDOF for the axial displacement... 

Initial experiments and theoretical studies to glue sticks in wood and the properties of the composite were carried out about 25 years ago. After basic considerations about the technology and the failure modes the first investigations concerned the stress distribution along the shear connection. At the beginning, the diameter of the boreholes was smaller than the rod diameter to create an additional mechanical bond between the bar and the wood. This changed in the late 1980s to the pure adhesive bond form (Portner and Seim 2008). 

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